A bone graft substitute (BGS) refers to a graft material that is used to substitute for bone tissue defects caused by various dental diseases or traumas, disease-related degeneration or other loss of tissue, so as to fill pore spaces in the bone tissue and to promote the formation of new bone. The best graft is generally known to be autogenous bone graft, but the autogenous bone graft has problems in that it requires a secondary surgical operation, is difficult to obtain the required amount, is difficult to carry out at small-scale hospitals, and has a possibility that makes patient's pain and morbidity severe.
For this reason, various substitutes, including donated human bones, artificial bones, and artificially synthesized materials made of bone hydroxyapatite, have been used for grafting. Commercially available bone substitutes are advantageous in that they are available in various forms, including powder, gel, slurry/putty, tablets, chips, morsels, pellets, sticks, sheets and blocks, are homogeneous, have a low risk with respect to infection and disease, eliminate the risk of pains resulting from the collection of a patient's own bones for grafting, and have reduced limitations on size. However, these commercial bone substitutes have various problems. For example, because their structure is significantly different from the physical structure of human bone, they have a slow tissue regeneration rate.
In an attempt to solve these problems, bone minerals obtained by physicochemically treating animal bones having a structure similar to that of human bones so as to remove organic substances have been processed such that they could be used in dental or orthopedic surgical operations. A typical example thereof may include Bio-Oss® commercially available from Geistlich Biomaterials.
A method for preparing said bone graft substitute using animal bones comprises the steps of: treating the thighbone of a bovine animal in a solvent having a boiling point of 80-120° C. to remove lipids; adding ammonia or primary amine to the treated bone to remove proteins and organic substances, thus obtaining bone mineral; and heating the bovine mineral at a high temperature of 250-600□ for a few hours, followed by drying (U.S. Pat. Nos. 5,167,961 and 5,417,975).
Although there was an example where a cartilage was treated with sodium hypochlorite to selectively remove the collagen phase in order to observe the remaining cartilage structure (Broz, J. J. et al., J. Mater. Sci. Mater. Med., 8:395, 1997), it has not yet been reported that sodium hypochlorite is used to remove all proteins in the preparation of bone minerals.
Among such animal bones, the most frequently used bone is bovine bone, and said Bio-Oss® product is also produced using the bovine bone as a raw material. However, as the onset of bovine spongiform encephalopathy has recently been frequent, the safety of the bovine bone as a raw material with respect to bovine spongiform encephalopathy is not ensured. For this reason, in a step of processing bovine bone into a bone graft material, a prion that causes bovine spongiform encephalopathy must be removed. Because the prion is not completely removed even at a high temperature of 600° C., it cannot be removed by methods known so far, and thus the development of a novel method is required.
Accordingly, the present inventors have prepared a bone graft substitute, which does not have the risk of bovine spongiform encephalopathy, using a method comprising the steps of inactivating prion protein with sodium hypochlorite in a process of preparing a bone graft substitute using bovine bone, and heating the resulting bone at a high temperature of 600° C., thereby completing the present invention.